Compressor anti-slugging device



April 1965 S.L.QU1GGLE ETAL 3,

COMPRESSOR ANTISLUGGING DEVICE Filed April 12, 1963 FIG! INVENTORSI STANLEY L. QUIGGLE FRANCIS W. OSBORN United States Patent 3,180,567 COMPRESSOR ANTI-SLUGGHNG DEVICE Stanley L. Quiggle and Francis W. Osborn, Wichita, Kane, assignors to The Coleman Company, Inc., Wichita, Kans, a corporation of Kansas Filed Apr. 12, 1963, Ser. No. 272,709 3 Claims. (Cl. 230-406) This invention relates to a compressor anti-slugging .device, and more particularly to the combination of such a device with a refrigeration compressor unit of the hermetically-sealed type. The anti-slugging device of this invention is especially adapted for protecting a refrigeration compressor under start-up condition-s.

The tendency for a refrigeration compressor to pump slugs of liquid refrigerant, with consequent damage to the pistons and valve mechanism, is well known in the refrigeration and air conditioning industry. This problem is particularly acute in refrigeration systems where the compressor and condenser units are remotely located with respect to the evaporator unit. Such a condition is frequently encountered in the air conditioning of homes where the condenser and compressor units are installed outside of the house, and the evaporator cooling coil-s are installed inside the furnace or the air distribution ducts of the house. In such situations, the lines or conduits connecting the units to form the complete system for circulation of the refrigerant will necessarily contain a large volume of refrigerant.

When the compressor unit is located where it will be exposed to low temperatures, for example, when it is installed outdoors, and the evaporator unit and other components are located indoors or where they would be exposed to higher temperatures, there is a tendency under shutdown and non-operating conditions for the refrigerant charge to accumulate as a liquid in the compressor. This would be particularly true during the colder months of the year, with an outside compressor unit. This problem. is further aggravated by the fact that as the outdoor temperature rises, the compressor unit, having greater thermal mass than other components of the system, Will remain cold longer and thereby tend to accumulate even more of the liquefied refrigerant. As will be understood, these conditions may frequently prevail at a time when it is desired to start up the air conditioning system after a long period of inactivity, as might occur in the early part of the spring. At such a time, however, there'is great danger that the accumulation of liquid within the compressor casing will cause slugging'of the compressor valves and pistons, and thereby result in serious damage, which ,will require servicing of the compressor and replacement of valves and other parts before the system can be placed in operation.

Hermetically sealed compressor units are most commonly employed in systems of the type described above Where the compressor unit is installed outdoors. Such compressor units are mounted within a casing which provides a sump in the bottom portion thereof for collection of the refrigerant, and oil which circulates therewith. .The volume of this sump, however,'is quite limited, and where the compressor unit is remotely located, as described above, the volume of the refrigerant charge in the system, including particularly the quantity of refrigerant in the connecting lines, would be much greater than the volume of the compressor sump. So-called high speed, hermetically-sealed compressor units are designed to operate at higher speeds with a view to providing the same compressor capacity but with smaller size andweight of the compressor unit. The reduced size of the high speed-type compressor means that the sump volume is even further reduced, and this further "ice increases the likelihood of compressor slugging under start-up conditions where the compressor unit is or has been at acolder temperature than the other components of the system.

It is, therefore, a general object of this invention to provide a compressor anti-slugging device which substantially overcomes the problems and difliculties described above. More specifically, it is an object of this invention to provide an anti-slugging device for use in combination with a hermetically-sealed refrigeration compressor unit which can be located outdoors while the evaporator cooling coils of the system are located indoors. A further object is to provide an anti-slugging device of the character described which can be used in combination with high speed, hermetically-sealed compressors. Further objects and advantages will be indicated in the following detailed specification.

This invention is shown in an illustrative embodiment in the accompanying drawing, in which:

FIGURE 1 is a side elevational view of an expansion tank which is designed for use in combination with a compressor unit in accordance with the present invention, a portion of the side wall of the tank being broken away toshow the construction of the internal components;

FIGURE 2 is a side elevational view illustrating somewhat schematically the way in which the tank of FIG. 1 would be integrated with a typical compressor unit, FIG. 2 illustrating particularly the condition just prior to start-up of the compressor after a period of shutdown, with the compressor unit at a colder temperature than other components of the air conditioning system;

FIGURE 3 is a schematic view similar to FIG. 2, illustrating particularly a condition which might exist during the initial start-up period; and

FIGURE 4 is another schematic view similar to FIGS. 2 and 3, illustrating particularly the condition which would exist as the compressor unit approached normal operation. p g

The anti-slugging device of this invention, which is illustrated particularly in FIG. 1 of the drawing, is designed for use in combination with a refrigeration compressor unit, which may be of the high speed type, and wherein the compressor and motor assembly is mounted within a casing which provides a hermetically-sealed, vertically-extending chamber. For example, such a compressor unit is shown somewhat schematically in FIG. 2. As'there shown, thecompressor and motor assembly is designated by the number 10, the casing by the number 11, and the chamberftherein by the number 12. Since the construction of such hermetically-sealed, motor driven compressors is well known in the art, it is not believed necessary to illustrate it in greater detail herein.

In accordance with the usual practice, the compressor unit of FIG. 2 includes a refrigerant vapor intake 13 which communicates with the upper portion of chamber 12. The lower portion of chamber 12 provides a sump, as indicated at 12a, for the collection of oil and/ or liquefied refrigerant. As is well known in the art, lubricant oil circulates throughout the system with the refrigerant, and an oil level is maintained within sump 12a during the normal operation of the compressor. For example, in normal operation the oil level in sump 12a might be as indicated in FIG. 4.v

Turning now more particularly to a discussion of the anti-slugging -device, as shown in detail in FIG. 1, the device includes a hermetically-sealed tank 14 which provides a vertically-extending expansion chamber 15 therein. It

will "be understood that tank 14 should be fabricated as a' the top' of tank 14, andthis arrangement is preferred.

areas-e7 The lower portion of tank 14 provides a sump for collec- 7 tion of liquid refrigerant and oil, particularly under shutdown conditions. Under such conditions, the system may appear as indicated in FIG. 2, where a relatively high liquid level is shown in the bottom portion of tank 14, the liquid being designated by the letter A. At this stage, the liquid A will consist primarily of liquefied refrigerant, but it will also contain a small amount of oil. The sump 12a of the compressor unit will also contain a relatively high level of liquid A, which will consist primarily of refrigeranttogether with a somewhat larger quantity of oil.

In accomplishing the objectives of the present invention, it is important to'dispose tank 14 in relation to casing 11 so that the lower or sump-providing portion of tank 14 is in horizontally-opposed relation to the lower orsumpproviding portion of the compressor unit casing 11. The desired relation of the units is indicated in FIG. 2. For best operation, it is also preferred to dispose tank 14 in close proximity to casing 11, although the distance between the casing and the tank can range from a few inches up to several feet while still accomplishing the puiposes of this invention. For optimum results, however, casing 11 and tank 14 should be located as close together. as conveniently possible.

In accordance with the present invention, there is "also provided a conduit or connecting pipe 17 which extends between tank 14 and casing 11, as indicated in FIG. 2. For example, the connecting conduit 17 may be C011? structed as shown in FIG. 1. The side wall of tank 14 is provided with an outlet fitting 18 which is joined to a nipple connector 19 on the side wall of casing 11. Since conduit 17 is designed to provide an open vapor space communication between chambers 12 and 15 under all I conditions, it is preferred that conduit 17 extend substantially horizontally between tank 14 and casing 11. Conduit 17 is also preferably located at an intermediate level with respect to both tank 14 and casing 11, as indicated in FIG. 2. In the illustration given, conduit 17 connects to the middle portion of the side wall of casing 11, while it connects totank 14a little above the middle thereof. Of course, tank 14 can be extended further above the level of conduit 17, but this will usually not be necessary. As indicated more clearly in FIG. 2, conduit 17 is located at a level immediately above the sump-providing portions of tank 14 and casing 11. The method of operation achieved by this construction and arrangement will subsequently be described.

Since some oil will accumulate in the bottom of tank 14 during normal operation, it is desirable to provide some means for transferring the oil from the bottom of tank 14 into the sump of casing 11. This can conveniently be accomplished by providing a liquid aspirating means disposed within tank 14 and arranged for drawing liquid from the lower portion thereof by the suction action of the refrigerant gas flowing through conduit 17. More particularly, this aspirating means should be arranged so that it will discharge the aspirated liquid, such as the oil, into conduit 17 for flow along the bottom thereof into-casing 11. I

An aspirating means of the desired type is shown in FIG. 1. It consists of a horizontally-extending conduit section'ztt which connects to the inner end of outlet fitting 18, and. extends across the upper portion of chamber 15. The conduit section 2% terminates in a vapor inlet 21..

Adjacent inlet 21 there is provided a dip tube 23, which vapor flowing through conduit section 21 and into-the con-v necting conduit 17 will create a suction effect which will cause liquid to be drawn upwardly within dip tube 23 and discharged-into the lower portion of the inner wall of conduit section 20. The velocity flow of the vapor will thencause the liquid to move along, with it through the connecting conduit 17 for discharge into chamber 12, thereby transferring the liquid to the sump portion of casing 11.

Operation 1 The operation of the anti-slugging device will now be described, with particular reference to start-up conditions where the compressor unit hasbeen at a colder temperature than the rest of the system, and consequently a large portion of the refrigerant charge has accumulated as a liquid in the vicinity of the compressor unit. Such a condition is illustrated in FIG. 2. The total volume of the accumulated liquid is represented by the liquid volume A in the compressor sump 12a, and by the liquid volume A in the lower portion of tank 1d. For example, this total volume might equal that of substantially all of the refrigerant charge. of the system.

In the illustration given, some margin of safety is provided for; The accumulated volume of liquid A in tank 14 might be somewhat higher, while still achieving the results of this invention. For example, the liquid volume A could be increased up to, but not above, the level of the connecting conduit 17. lfliquid was permitted to accumulatein tank 14 'to a level above the connecting conduit 17, the passage through the connecting conduit would be liquid-sealed, and the vapor spaces respectively within the upper portions of casing 1-1 and tank 14 would no longer be. in communication. Insuch a circumstance,

the higher vapor pressure within the upper 'por-tion'of tank 14, as couldeasily occur under start-up conditions,

might cause an excessive volume of liquid to'be forced from tank 14 through connecting conduit 17 into casing 1-1, thereby raising the level of liquid in casing 11 temporarily above that of conduit 17; Such an increase could lead to slugging of the compressor valves, thereby defeating the purpose of this invention; Under start-up conditions, the rapid application of reduced pressure and suction to the liquid'refrigerant will usually cause considerable frothing and foaming of the refrigerant. Therefore, unless the. level of the liquid refrigerant within tank 14 is kept well. below.- conduit :17, slugs of liquid may be carried through the conduit athigh velocity, passing upwardly into the top. portion of chamber 12 to the vicinity of the compressor intake 13. Here, again, undesirable slugging of the compressor canresult. It will, therefore, be understood that the combined volumes of the sump portions of the compressor casing and tank 14, being the portions below conduit 17, should. at least equal the total volume of refrigerant in the system when completely liquefied. Of course, under most conditions, not all of At the same time, however, the. vapor spaces within casing 11 and tank 14 will remain in open communication so thatthere is no pressure differential between the vapor spaces. When the. compressor-is started, refrigerant vapor is drawn in through intake 13 from the vapor space within casing 11. The liquefied refrigerant which is collected with-in casing 11gand tank 141will. be. rapidly converted'to vapor, and suction from .the. compressor will also be communicated to line 16 for establishing the usual refrigerant flow in the system. It will, therefore, immediately begin to. flow through conduit 17 from tank 14 into casing 11. As previously described, this vapor flow will have an aspirating actionwith respect to dip tube 23 and liquid will be drawn up through this tube, from the bottom of tankld and pass along the bottom of conduit 17 into the sump-1-2a,l This transfer of liquid, together Ann. A

with the vaporization of the liquid refrigerant, will rapidly reduce the liquid level within tank 14. For example, in a very short time the relative liquid levels may appear as indicated in FIG. 3.

Within a few minutes, the refrigerant will be fully vaporized, and the system will be in normal operation. Under normal conditions, when the compressor is operating in the regular manner, there will be little or no liquefied refrigerant in either tank 14 or casing 11. The only liquid within these units will be the oil which to some extent circulates with the refrigerant, but collects primarily in the sump 12a of the compressor unit. At this time, the system might appear as indicated in FIG. 4 where the liquid A in sump 12 is substantially entirely oil. Since some oil circulates with the refrigerant, the oil being soluble in the refrigerant, some oil will collect in the bottom of tank 14. This will be kept to very low level by the action of dip tube 23, which will transfer the collected oil from tank 14 to sump 12a, as previously described.

In FIGS. 2, 3 and 4, flow arrows have been applied, and these arrows are further designated by either the letter V or the letter L. The letter V indicates vapor flow, while the letter L indicates liquid flow. In FIG. 2, flow arrows are indicated as extending in both directions for both liquid and vapor flow through conduit 17. As previously explained, such flow may occur prior to or during start-up of the compressor. Under normal operating conditions, the flow arrows will appear as shown in FIGS. 3 and 4. Under such conditions, there will normally be no liquid or vapor flow from casing 11 through conduit 17 into tank 14.

While in the foregoing specification this invention has been described in relation to a preferred embodiment thereof, and many details have been set forth for the purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.

We claim:

1. In combination with a refrigeration compressor unit mounted within a casing providing a chamber therein, the compressor of said unit having a refrigerant vapor intake communicating with the upper portion of said chamber, the lower portion of said chamber providing a sump for collection of refrigerant liquid and oil, an antislugging device comprising a tank providing an expansion chamber therein, said tank being disposed with the lower portion thereof at approximately the same level as the sump-providing portion of said compressor casing, said tank being provided with an inlet above the bottom portion thereof for communicating with a vapor return line, the lower portion of said tank providing a sump for collection of liquid refrigerant and oil, a conduit extending between said casing and said tank at an intermediate level, said conduit providing an open communication between the upper portions of said casing and said tank, and means for transferring liquid from the bottom portion of said tank to the sump of said compresor unit, said conduit extending substantially horizontally between said casing and said tank, and said casing and said tank being located in close proximity to each other.

2. In combination with a refrigeration compressor unit mounted within a casing providing a hermeticallysealed, vertically-extending chamber, the compressor of said unit having a refrigerant vapor intake communicating with the upper portion of said chamber, the lower portion of said chamber providing a sump for collection of refrigerant liquid and oil, an anti-slugging device comprising a tank providing a vertically-extending expansion chamber therein, said tank being disposed with the lower portion thereof in horizontally opposed relation to the lower portion of said casing, the upper portion of said tank providing an inlet for communicating with a vapor return line, the lower portion of said tank providing a sump for collection of liquid refrigerant and oil, a conduit extending between said casing and said tank at an intermediate level with respect to both said casing and said tank, said conduit providing open communication between said casing chamber and said expansion chamber immediately above the sump-providing portions thereof, and liquid aspirating means disposed within said expansion chamber for drawing liquid from the lower portion thereof by the suction action of the gas flowing through said conduit and transferring said liquid into said casing chamber, said conduit extending substantially horizontally between said casing and said tank, and said tank and said casing being located in close proximity to each other.

3. In combination with a high speed refrigerator compressor unit mounted within a casing providing a hermetically-sealed, vertically-extending chamber, the compressor of said unit having a refrigerant vapor intake communieating with the upper portion of said chamber, the lower portion of said chamber providing a sump for collection of refrigerant liquid and oil, an anti-slugging device specially adapted for protecting said compressor under start-up conditions, comprising a hermetically-sealcd tank providing a vertically-extending expansion chamber therein, said tank being disposed in close proximity to the casing of said compressor unit, with the lower portion of said tank in horizontally-opposed relation to the lower portion of said casing, the upper portion of said tank providing an inlet for communicating with a vapor return line, the lower portion of said tank providing a sump for collection of liquid refrigerant and oil, a conduit extending substantially horizontally between said casing and said tank at an intermediate level with respect to both said casing and said tank, said conduit providing open communication between said casing chamber and said expansion chamber immediately above the sump-providing portions thereof, and liquid aspirating means disposed within said expansion chamber for drawing liquid from the lower portion thereof by the suction action of the refrigerant gas flowing through said conduit into said casing chamber, said aspirating means discharging liquid into said conduit for flow along the bottom thereof into said casing chamber.

References Cited by the Examiner UNITED STATES PATENTS 1,940,734 12/33 Shipman 62-83 2,760,355 8/56 Swart 6283 2,956,730 10/60 Hamilton et al 230-58 LAURENCE V. EFNER, Primary Examiner.

ROBERT M. WALKER, Examiner. 

1. IN COMBINATION WITH A REFRIGERATION COMPRESSOR UNIT MOUNTED WITHIN A CASING PROVIDING A CHAMBER THEREIN, THE COMPRESSOR OF SAID UNIT HAVING A REFRIGERANT VAPOR INTAKE COMMUNICATING WITH THE UPPER PORTION OF SAID CHAMBER, THE LOWER PORTION OF SAID CHAMBER PROVIDING A SUMP FOR COLLECTION OF REFRIGERANT LIQUID AND OIL, AN ANTISLUGGING DEVICE COMPRISING A TANK PROVIDING AN EXPANSION CHAMBER THEREIN, SAID TANK BEIG DISPOSED WITH THE LOWER PORTION THEREOF AT APPROXIMATELY THE SAME LEVEL AS THE SUMP-PROVIDING PORTION OF SAID COMPRESSOR CASING, SAID TANK BEING PROVIDED WITH AN INLET ABOVE THE BOTTOM PORTION THEREOF FOR COMMUNICATING WITH A VAPOR RETURN LINE, THE LOWER PORTION OF SAID TANK PROVIDING A SUMP FOR COLLECTION OF LIQUID REFRIGERANT AND OIL, A CONDUIT EXTENDING BETWEEN SAID CASING AND SAID TANK AT AN INTERMEDIATE LEVEL, SAID CONDUIT PROVIDING AN OPEN COMMUNICATION 